It is known in the art relating to drive systems for diesel electric locomotives and the like to provide a railway truck mounted axle hung electric traction motor partially supported upon and geared to a drive axle by engaged pinion and drive gears. The gears are lubricated by a fluid lubricant contained in a gear case surrounding the gears on the pinion end of the traction motor and on the axle.
Generally in American locomotives it has been the practice to use a heavy grease-like lubricant which is relatively easily contained, and the gear cases comprise inexpensive two piece sheet metal stampings containing simple seals at the motor shaft and axle openings. European style locomotives, on the other hand, generally utilize a light oil-like lubricant which is contained by more elaborate labyrinth seals mounted in expensive heavy duty gear cases with accurately machined seal supporting surfaces. Some of these arrangements may also contain either an idler gear or two steps of gear reduction, both with additional bearings. For the latter types the gear case is even more complex and expensive. Due to the usage of improved three-phase traction motors having bearings which are conveniently lubricated via the gear case, a light lubricant is becoming desirable even in American locomotives.
A distinct advantage of the sheet metal gear case is the ease of repair or inexpensive replacement in the event of damage. The heavy duty gear cases which may be aluminum castings, for example, and may also be structural members with additional bearings, are not readily repairable and replacement is extremely expensive and time-consuming. The bottom of the gear case, which may be about 4 inches above the rail elevation, is the lowest part of the locomotive other than the wheels. Occasional minor derailments of locomotives do occur and frequently result in damage to the gear case whether it is made of sheet metal or castings. Thus there is a need for a gear case which is suitable for containing light lubricants and at the same time can sustain impact to the bottom of the gear case without damage which is expensive or difficult to repair.